How to Replace the Serpentine Belt on a 2018 Subaru Legacy (Step-by-Step Guide)
Tools, parts list, safety tips, belt routing, and final checks to stop squeal and slipping for 2015, 2016, 2017, 2018, 2019
How to Replace the Serpentine Belt on a 2018 Subaru Legacy (Step-by-Step Guide)
Tools, parts list, safety tips, belt routing, and final checks to stop squeal and slipping for 2015, 2016, 2017, 2018, 2019
🔧 Legacy - Serpentine Belt Replacement
The serpentine belt drives key accessories like the alternator and A/C. If it’s cracked, noisy, or slipping, replacement prevents charging problems and overheating.
Difficulty Level: Intermediate | Estimated Time: 0.8-1.5 hours
⚠️ Safety & Precautions
- ⚠️ Work on a cool engine; hot pulleys can burn you.
- ⚠️ Keep fingers, hair, and clothing away from the belt path.
- ⚠️ Do not start the engine with tools in the engine bay.
- ⚠️ If you raise the front of your Legacy, support it with jack stands on solid ground.
- ⚠️ Battery disconnect is not required, but remove the key and keep it away from the car.
🔧 Required Tools
You'll need the following tools for this repair:
- 3/8" drive ratchet
- 3/8" drive breaker bar
- 14mm socket
- 10mm socket
- 6" extension for 3/8" drive
- Trim clip removal tool
- Flathead screwdriver
- Torque wrench (10-80 ft-lbs range)
- Flashlight
- Mechanic gloves
- Safety glasses
- Floor jack (rated 2-ton minimum)
- Jack stands (rated 2-ton minimum)
- Wheel chocks
🔩 Required Parts
HowToo sells all the parts you need for this repair:
- Serpentine belt - Qty: 1
- Plastic undertray clips - Qty: 4
📋 Before You Begin
- Park on level ground, shift to Park, and set the parking brake.
- Place wheel chocks behind the rear wheels.
- Take a quick photo of the belt routing, or locate the belt-routing sticker under the hood.
- If access is tight, raise the front with a floor jack and support with jack stands.
🔨 Step-by-Step Instructions
Follow these steps in order:
Step 1: Remove the lower splash shield (if equipped)
- Use floor jack (rated 2-ton minimum) and jack stands (rated 2-ton minimum) to safely support the front.
- Remove the undertray fasteners using a trim clip removal tool and 10mm socket.
- Lower the shield and set it aside.
Step 2: Locate the belt tensioner
- Use a flashlight to find the automatic belt tensioner at the front of the engine.
- The tensioner is spring-loaded; it pivots to release belt tension.
- Take a photo before removing the belt.
Step 3: Release belt tension
- Install a 14mm socket on a 3/8" drive breaker bar.
- Place the socket on the tensioner’s hex and rotate the tensioner to relieve belt tension.
- While holding it released, slide the belt off the easiest pulley (usually the alternator pulley) by hand while wearing mechanic gloves.
- Slowly let the tensioner return to its resting position. Do not let it snap back.
Step 4: Remove the old belt
- Pull the belt out of the remaining pulleys by hand.
- Use a flashlight to inspect each pulley for wobble or roughness (spin by hand).
- If any pulley feels gritty or noisy, the tensioner or idler pulley may also need replacement.
Step 5: Route the new belt
- Compare the new belt to the old one for matching length and rib count.
- Route the belt around all pulleys except one easy-to-reach pulley last.
- Make sure the belt ribs sit fully in the grooved pulleys and the back of the belt rides on any smooth pulleys.
- Misalignment can shred a belt fast.
Step 6: Apply tension and seat the belt
- Use the 14mm socket and 3/8" drive breaker bar to rotate the tensioner and create slack.
- Slip the belt onto the last pulley, then slowly release the tensioner.
- Re-check every pulley with a flashlight to confirm the belt is centered and fully seated.
Step 7: Reinstall the splash shield
- Reinstall the undertray using a 10mm socket and trim clip removal tool.
- Snug fasteners with a 3/8" drive ratchet and 10mm socket.
Step 8: Final check
- Remove tools from the engine bay and lower the car using the floor jack (rated 2-ton minimum).
- Start the engine and watch the belt for 20-30 seconds.
- Listen for squeal or slapping sounds; shut off immediately if the belt walks off a pulley.
✅ After Repair
- Recheck belt alignment after a short 5-10 minute drive.
- If you hear chirping/squealing, inspect for a pulley that’s misaligned or a weak tensioner.
- Look under the car to confirm the splash shield is secure and not rubbing.
💰 DIY vs Shop Cost
Shop Cost: $160-$320 (parts + labor)
DIY Cost: $25-$60 (parts only)
You Save: $135-$260 by doing it yourself!
Shop labor rates vary but typically run $100-$150/hour. This repair takes a shop approximately 0.8-1.5 hours.
🎯 Ready to get started?
HowToo makes it easy: same-day/2-day shipping on every part, plus all the tools and specialty tools you need! Check out the parts and tools sections below to add everything to your cart.

















